The present invention relates to a hydrophilic colloid composition e.g. a composition for the coating of a layer in a photographic element.
Photographic coating compositions containing aqueous gelatin and high levels of anionic surfactants are prone to exhibit high viscosity, either as simple melts or as more complex melts such as dispersions of relatively hydrophobic materials (e.g. oil) where the anionic surfactant is used as the dispersing aid. In the simple melt case, rheological properties tend to be Newtonian in behaviour. In the disperse system case, systems can be strongly non-Newtonian, exhibiting high viscosity at low shear and low viscosity at high shear. Such properties can adversely affect the transport and coating uniformity of these systems.
The addition of certain cationic or nonionic surfactants to these systems is known to reduce their viscosity and shear thinning behaviour, and can therefore be used to overcome problems of this kind. For example, U.S. Pat. No. 5,300,418 describes the use of specific nonionic surfactants for reducing the viscosity of photographic dispersions. GB-A-2 140 572 describes the use of specific cationic surfactants for reducing the viscosity of photographic dispersions.
There is a need for rheology modifiers in the above-mentioned compositions which are much more efficient at reducing low shear viscosity and shear thinning behaviour.
The invention provides a hydrophilic colloid composition having hydrophobic material dispersed therein and comprising an anionic surface active agent characterised in that the composition further comprises a cationic surface active agent in an amount sufficient to reduce the viscosity of the composition, the cationic surface active agent comprising a hydrophobic moiety, a non-ionic hydrophilic moiety and a cationic hydrophilic moiety.
Cationic surfactants containing polyethoxylate groups offer advantages over either cationic or nonionic surfactants as rheology modifiers in the above-mentioned compositions. In the simple melt case, they are more efficient at reducing viscosity than either the nonionic or cationic surfactants, and show better compatibility with the anionic surfactants than basic cationic surfactants insofar as they provide clear solutions as opposed to cloudy or phase-separating systems. In the case of disperse systems, they are much more efficient at reducing low shear viscosity and shear thinning behaviour.
The cationic surface active agent used in the composition of the invention as a rheology modifier comprises a hydrophobic moiety, a nonionic hydrophilic moiety and a cationic hydrophilic moiety.
The cationic hydrophilic moiety is preferably a quaternised nitrogen (N+) to which the other moieties are covalently bound.
The nonionic hydrophilic moiety is preferably one or two polyethoxylate groups.
The hydrophobic moiety is preferably a hydrocarbon group.
Preferred cationic surface active agents include compounds having the structure 
wherein
R1 is an alkyl, alkenyl, alkylaryl or arylalkyl chain having from 8 to 20 carbon atoms or a partially or fully fluorinated alkyl, alkenyl, alkylaryl or arylalkyl chain of equivalent hydrophobic strength e.g. having from 4-14 carbon atoms;
R2 is hydrogen, alkyl having from 1 to 8 carbon atoms e.g. methyl and n-butyl, or benzyl;
R3 is hydrogen or alkyl having from 1 to 4 carbon atoms e.g. methyl (preferably R3 is hydrogen if the sum of n and m is greater than 0;
Xxe2x88x92 is halide (preferably Brxe2x88x92 or Clxe2x88x92);
L represents a suitable linking chemistry between R1 and the positively charged nitrogen e.g. a covalent chemical bond or xe2x80x94(CH2CH2O)xxe2x80x94;
each m and n independently is 0 or an integer such that m+n is 2 to 30, preferably 5 to 30, more preferably 12 to 18 and most preferably 15; and,
X is an integer from 2 to 30, preferably 5 to 30, more preferably 12 to 18 and most preferably 15.
For preferred structures, L is xe2x80x94(CH2CH2O)xxe2x80x94 when m+n is 0, and each m and n independently is greater than 0 when L is other than xe2x80x94(CH2CH2O)xxe2x80x94. Preferred compounds include those wherein
R1 is an alkyl or alkylaryl group having from 10 to 20 carbon atoms;
R2 is alkyl having from 1 to 4 carbon atoms e.g. methyl and n-butyl;
R3 is hydrogen;
L represents a covalent chemical bond; and, m+n is 5 to 30, preferably 15.
Other preferred compounds include those wherein
R1 is an alkyl or alkylaryl group having from 10 to 20 carbon atoms;
R2 is alkyl having from 1 to 8, preferably 1 to 4 carbon atoms e.g. methyl and n-butyl;
R3 is alkyl having from 1 to 4 carbon atoms e.g. methyl;
each m and n independently is 0;
L represents xe2x80x94(CH2CH2O)xxe2x80x94;
x is an integer from 5 to 30, preferably 15.
Preferably, the cationic surface active agent is present in the composition in an amount from 0.1 to 0.5, more preferably from 0.2 to 0.4 equivalents relative to the amount of anionic surfactant present in the system.
A preferred hydrophilic colloid is gelatin e.g. alkali-treated gelatin (cattle bone or hide gelatin) and acid-treated gelatin (pigskin or cattle gelatin) or a gelatin derivative e.g. acetylated gelatin and phthalated gelatin. Other suitable hydrophilic colloids include naturally occurring substances such as proteins, protein derivatives, cellulose derivatives e.g. cellulose esters, polysaccharides e.g. dextran, gum arabic, zein, casein and pectin, collagen derivatives, agar-agar, arrowroot and albumin. Examples of suitable synthetic hydrophilic colloids include polyvinyl alcohol, acrylamide polymers, maleic acid copolymers, acrylic acid copolymers, methacrylic acid copolymers and polyalkylene oxides.
The hydrophobic material dispersed in the hydrophilic colloid composition may be any hydrophobic photographic addenda.
A number of hydrophobic photographic additives used in light sensitive photographic materials are oil-soluble and are used by dissolving them in a substantially water-insoluble, high boiling point solvent which is then dispersed in an aqueous hydrophilic colloid solution with the assistance of a dispersing aid. Such oil-soluble additives include image forming dye couplers, dye stabilizers, antioxidants and ultra-violet radiation absorbing agents. A typical solvent used to dissolve the additive is aromatic e.g. di-n-butyl phthalate.
In the following discussion of suitable materials for use in the compositions and materials of this invention, reference will be made to Research Disclosure, December, 1989, Item 308119, published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire, P010 7DQ, UK. This publication will be identified hereafter by the term Research Disclosure. 
Suitable methods of preparing photographic dispersions are described in Research Disclosure, Sections XIV A and XIV B. For example, homogenised oil in aqueous gelatin dispersions of photographic couplers can be prepared by dissolving the coupler in a coupler solvent and mechanically dispersing the resulting solution in an aqueous gelatin solution (see U.S. Pat. No. 2,322,027).
Alternatively, microprecipitated dispersions of photographic couplers prepared by solvent and/or pH shift techniques are becoming more widely used (see references: U.K. Patent No. 1,193,349; Research Disclosure 16468, December 1977 pp 75-80; U.S. Ser. No. 288,922 (1988) by K. Chari; U.S. Pat. Nos. 4,970,139 and 5,089,380 by P. Bagchi; U.S. Pat. No. 5,008,179 by K. Chari, W. A. Bowman and B. Thomas; U.S. Pat. No. 5,104,776 by P. Bagchi and S. J. Sargeant) and offer benefits in decreased droplet size and often increased reactivity relative to conventional oil-in-water homogenised dispersions.
Couplers which form cyan dyes upon reaction with oxidized color-developing agents are described in such representative patents and publications as U.S. Pat. Nos. 2,772,162; 2,895,826; 3,002,836; 3,034,892; 2,747,293; 2,423,730; 2,367,531; 3,041,236; and 4,333,999; and Research Disclosure, Section VII D.
Couplers which form magenta dyes upon reaction with oxidized color developing agents are described in such representative patents and publications as: U.S. Pat. Nos. 2,600,788; 2,369,489; 2,343,703; 2,311,082; 3,152,896; 3,519,429; 3,062,653; and 2,908,573; and Research Disclosure, Section VII D.
Couplers which form yellow dyes upon reaction with oxidized and color developing agents are described in such representative patents and publications as: U.S. Pat. Nos. 2,875,057; 2,407,210; 3,265,506; 2,298,443; 3,048,194; and 3,447,928; and Research Disclosures, Section VII D.
Couplers which form colorless products upon reaction with oxidized color developing agents are described in such representative patents as: UK Patent No. 861,138; U.S. Pat. Nos. 3,632,345; 3,928,041; 3,958,993; and 3,961,959.
The couplers can be dissolved in a solvent and then dispersed in a hydrophilic colloid. Examples of solvents usable for this process include organic solvents having a high boiling point, such as alkyl esters of phthalic acid (for example, dibutyl phthalate, dioctyl phthalate, and the like), phosphoric acid esters (for example, diphenyl phosphate, triphenyl phosphate, tricresyl phosphate, dioctyl butyl phosphate, and the like) citric acid esters (for example, tributyl acetyl citrate, and the like) benzoic acid esters (for example, octyl benzoate, and the like), alkylamides (for example, diethyl laurylamides, and the like), esters of fatty acids (for example dibutoxyethyl succinate, dioctyl azelate, and the like), trimesic acid esters (for example, tributyl trimesate, and the like), or the like; and organic solvents having a boiling point of from about 30xc2x0 to about 150xc2x0 C., such as lower alkyl acetates (for example, ethyl acetate, butyl acetate, and the like), ethyl propionate, secondary butyl alcohol, methyl isobutyl ketone, b-ethoxyethyl acetate, methyl cellosolve acetate, or the like. Mixtures of organic solvents having a high boiling point and organic solvents having a low boiling point can also be used.
Suitable anionic surface active agents may be chosen from any known anionic surface active agents. Examples of anionic surface active agents are as follows.
1. Sulphosuccinates having the general structure V(a): 
or V(b): 
wherein
each R1 independently is an alkyl, alkenyl, alkylaryl or arylalkyl chain having from 8 to 20 carbon atoms;
M+ is a suitable monovalent cation e.g. an alkali metal cation such as Na+, K+, Li+; ammonium; alkylammonium such as N(CH3)4+, N(C2H5)4+ and N(C3H7)4+; and,
n is an integer from 1 to 30.
Examples of compounds having structure V(a) are: Aerosol(trademark) 102 (Cyanamid; n=5, L=covalent bond, R1=a C10-C12 straight chain alkyl group); Sermul(trademark) EA176 (Servo BV; n=10, L=covalent bond, R1=nonylphenyl).
Examples of compounds having structure V(b) are: Aerosol(trademark) MA (Cyanamid; R1=hexyl); Aerosol(trademark) OT (Cyanamid; R1=2-ethyl-hexyl); and the compound described in U.S. Pat. No. 4,968,599 (R1=n-C3F7CH2).
2. Phosphates having the general structure VI: 
wherein
R1 is an alkyl, alkenyl, alkylaryl or arylalkyl chain having from 8 to 20 carbon atoms;
L is a simple linking group such as xe2x80x94Oxe2x80x94 or a covalent bond;
M+ is a suitable monovalent cation e.g. an alkali metal cation such as Na+, K+, Li+; ammonium; alkylammonium such as N(CH3)4+, N(C2H5)4+ and N(C3H7)4+; and,
n is an integer from 1 to 30.
Examples of compounds having structure VI are: Sermul(trademark) surfactants EA211, EA188, and EA205 (Servo BV, R1=nonylphenyl, L=xe2x80x94Oxe2x80x94, M+=Na+, and n=6, 10, and 50, respectively).
3. Sulphates having the general structure VII:
R1L(OCH2CH2)nxe2x80x94Oxe2x80x94SO3xe2x88x92M+
wherein
R1 is an alkyl, alkenyl, alkylaryl or arylalkyl chain having from 8 to 20 carbon atoms or a fluoroalkyl group having 4 to 14 carbon atoms
L is a simple linking group such as xe2x80x94Oxe2x80x94 or a covalent bond;
M+ is a suitable monovalent cation e.g. an alkali metal cation such as Na+, K+, Li+; ammonium; alkylammonium such as N(CH3)4+, N(C2H5)4+ and N(C3H7)4+; and,
n is 0 or an integer from 1 to 30.
Examples of compounds having structure VII are: sodium dodecyl sulphate (R1=dodecyl, n=0); Sermul(trademark) surfactants EA54, EA151, EA146 (Servo BV, R1=nonylphenyl, L=covalent bond, M+=Na+ and n=4, 10, and 15, respectively); Polystep(trademark) B23 (R1=dodecyl, and n=10); sulphated derivatives of Brij(trademark) 76 and 78 (ICI, R1=C18H37 (average), L=covalent bond, and n=10 and 20, respectively).
4. Sulphonates having the general structure VIII:
R1L(OCH2CH2)nSO3xe2x88x92M+
wherein
R1 is an alkyl, alkenyl, alkylaryl or arylalkyl chain having from 8 to 20 carbon atoms;
L is a simple linking group such as xe2x80x94Oxe2x80x94 or a covalent bond;
M is a suitable monovalent cation e.g. an alkali metal cation such as Na+, K+, Li+; ammonium; alkylammonium such as N(CH3)4+, N(C2H5)4+ and N(C3H7)4+; and,
n is 0 or an integer from 1 to 30.
Examples of compounds having structure VIII are: Triton(trademark) X-200 (Rohm and Haas, R1=t-octylphenyl, L=covalent bond, n=2-4 nominal and M+=Na+); FT248(trademark) (Bayer, R1=perfluorooctyl, L=covalent bond, n=0 and M+=N(C2H5)4+); and Alkanol XC(trademark) (DuPont, R1=triisopropyl naphthalene, L=covalent bond, n=0 and M+=Na+).
5. Fluorocarboxylates having the general structure IX:
R1COOxe2x88x92M+
wherein
R1 is a fluoroalkyl chain having from 6 to 9 carbon atoms e.g C7F15, C8F17 and C9F19; and,
M+ is a suitable monovalent cation e.g. an alkali metal cation such as Na+, K+, Li+; ammonium; alkylammonium such as N(CH3)4+, N(C2H5)4+ and N(C3H7)4+.
Preferably, the anionic surface active agent is present in the composition in an amount from 0.5 to 2.0, more preferably from 0.7 to 1.2 percent by weight based on the weight of the total system.
In accordance with the invention, a method of preparing a multilayer photographic material comprises
(a) simultaneously coating on a support a plurality of aqueous hydrophilic colloid layers including at least one light-sensitive silver halide emulsion layer wherein at least one of the hydrophilic colloid layers comprises a composition according to the invention and,
(b) drying the coated layers.
The invention is further illustrated by way of example as follows.
Details of materials used in the specific examples are as follows.

Viscosity of Simple Aqueous Gelatin Melts
Anionic surfactants tend to cause large increases in solution viscosity when added to aqueous gelatin melts (solutions) above their critical micelle concentration. This has been well demonstrated for a homologous series of alkyl sulphates (J Greener, B A Contestable, M D Bale, Macromolecules, 20, 2490, (1987)). It is known from the prior art references, that either nonionic or cationic surfactants can be added to such systems to lower the viscosity of the melt to aid their coating or transport. To test the materials of this invention a base standard solution was adopted as a point of reference. The base standard chosen was 1% w/w of the anionic surfactant Alkanol XC in aqueous gelatin solution containing 10% w/w deionised Type IV bone gelatin. This resulted in a base standard solution viscosity of 100 mPa s (at a shear rate of 23 sxe2x88x921) The molarity of the base standard solution was measured to be 23 milli-molar (mM) by Epton titration with hyamine. Other surfactants were then incorporated into individual base standard solutions at two molar levels and the viscosities of the resultant solutions were measured. The molar levels selected were 6.9 mM and 20.7 mM which correspond to 0.3 and 0.9 equivalents wrt the anionic surfactant (Alkanol XC) in the base solution. The results are presented in Table 1.
Table 1 shows clearly that the nonionic/cationic (ethoxylated cationic) class of surfactant gives certain advantages over the other surfactant classes:
i) They reduce the viscosity of anionic surfactant/gelatin systems more efficiently than the cationic, nonionic or nonionic/anionic (ethoxylated anionic) classes.
ii) As cationic species per se, they reduce viscosity without causing any phase separation (cloudiness), i.e. they show superior compatibility in solution with anionic surfactants than do simple cationics.
The following experimental methods were used to prepare materials used in the Example of the invention:
Preparation of 2 kg Homogenised Dispersion Containing Coupler C1
258 g of coupler C1 was dissolved in a mixture of 65 g di-n-butyl phthalate and 65 g of solvent S1 at 145xc2x0 C. to make Solution A. 176 g of gelatin was dissolved in 1196 g of water containing 176 g of an aqueous solution of Alkanol XC containing 17.6 g of Alkanol XC and 31 g of propionic acid/sodium propionate preservative to make Solution B. After heating Solution B to 80xc2x0 C., Solution A was added to Solution B and the whole mixture was immediately homogenised for 5 minutes at 10,000 rpm with a Kinematica Polytron homogeniser fitted with a 35 mm diameter head. The homogenised mixture was then passed twice through a Microfluidics Microfluidiser (model no. 110E) which was run at 10,000 psi pressure and a water bath temperature of 75xc2x0 C. to give the final dispersion.
Preparation of 1.7 kg Homogenised Dispersion Containing Coupler C2
149 g of coupler C1 was dissolved in a mixture of 58.5 g di-n-butyl phthalate, 22.3 g of solvent S1, 79.1 g of stabiliser S2 and 14.9 g of scavenger S3 at 145xc2x0 C. to make Solution C. 149 g of gelatin was dissolved in 1032 g of water containing 164 g of an aqueous solution of Alkanol XC containing 16.4 g of Alkanol XC and 32.7 g of propionic acid/sodium propionate preservative to make solution D. After heating Solution D to 80xc2x0 C., Solution C was added to Solution D and the whole solution was immediately homogenised for 5 minutes at 10,000 rpm with a Kinematica Polytron homogeniser fitted with a 35 mm diameter head. The homogenised mixture was then passed twice through a Microfluidics Microfluidiser (model no. 110E) which was run at 10,000 psi pressure and a water bath temperature of 75xc2x0 C. to give the final dispersion.
Sample Preparation of Disperse Systems
The total amount of sample prepared was 10 g. This comprised 1 g aqueous surfactant solution and 9 g dispersion. The surfactant solution was prepared by weighing the desired amount of surfactant to give appropriate molar equivalence to the Alkanol XC in the dispersion and making the weight up with water.
The dispersion was heated at 45xc2x0 C. until it had melted (approximately 20 minutes), then the surfactant solution was added and the mixture was shaken to ensure complete and rapid mixing. The resultant mixtures were heated at 45xc2x0 C. for a further hour, after which time the flow curve was measured. Throughout, care was taken to ensure no air entered the system.
Measurement of Viscosity
The rheological measurements were made on two computer-controlled rheometers made by Bohlin Instruments, the Bohlin VORxe2x80x94a controlled-strain rheometer and the Bohlin CS50xe2x80x94a controlled-stress rheometer, both very versatile instruments. The small volume sample cell, C2.3/26 (bob-and-cup geometry), or the double concentric cylinder, DG 24/27 was used for the measurements. Flow curves (viscosity as a function of applied shear) were recorded to xcx9c1000 sxe2x88x921 from stresses of  less than 0.1 Pa.
For the experiments, 2 ml of sample was placed into the cup using a syringe. The bob, which was pre-warmed, was then lowered to the correct position and the sample sheared. A low viscosity silicone oil was placed on top of the sample to prevent formation of a surface film of dried gelatin. A cover was placed the measuring geometry to provide further thermal insulation. The sample was allowed to come to thermal equilibrium for a few minutes before the rheological experiments were performed. There appeared to be no shear-history dependence. All measurements were carried out at 42xc2x0 C.